Jan. 189S.] BOTANICAL SOCIET^T OF EDINBUEGII 101 



Stand in comparison with A, are the slight falls in 1869, 

 '74, and '80, also a rise, instead of a fall, from 1870 to 

 1872, and in 1891, but as the positions and exposures of 

 the trees were so difterent, the latter, situated low down in 

 the valley, would be more affected by frosts than the trees 

 on the hillsides. 



When we compare the curves of the three larches A, 

 F, and G, we find that they have maxima in common in 

 1859, '75, '82, '89, and '93 ; but the only minima which 

 strictly agree are in 1888. 



The Norway spruce, B, shows a good curve. It is known 

 to be a tree which thrives best in a moist atmosphere, and 

 with a certain amount of shade. 



The increment increased from 1856 to 1857, as the 

 former was a remarkably cold season, and the latter a very 

 fine one, with rainfall about the mean. 



The fall and rise from 1857 to 1861 corresponded with 

 the drought of those years. The warm, humid, rainy season 

 of 1861 produced the largest increment of the 38 years. 



The fall from 1861 to 1866 agreed with a dry period. 

 The rise of 1867 occurred during greater rainfall and 

 humidity, and with sunshine below the mean. 



The rise begun in 1867 was maintained until 1870, when 

 the seasons were warm and humid, although the rainfall 

 was below the mean. 



The fall of 1871 was probably due to low summer 

 temperature. The rise from 1871 to 1875 was due to 

 very wet but warm summers; and although 1875 was 

 drier than any of the preceding five years, yet the warm 

 summer maintained the growth, and the rainfall and 

 humidity were only slightly below the mean. The summer 

 rainfalls of 1872-73 were probably too great even for the 

 wellbeing of a moisture-lover like spruce. 



The fall from 1875 to 1878 was due to the drought of 

 1876 and the very low summer temperature of 1877. 



The better conditions of 1878 prevented a further 

 decrease of increment, and helped to counteract the influence 

 of the cold summer of 1879, when there was a slight rise 

 over the increment of 1878. 



The higher temperature of 1880 caused an increase in the 

 increment, and the rainfall was only a little under the mean. 



